1. Field of the Invention
The present invention relates to the fields of electronics and computer systems. More specifically, the present invention relates to DC-DC converters having specific applications in computer systems.
2. Background Information
The power supplies in a computer system are designed to meet the specific power requirements of the integrated circuit chips (ICs) that are the components of the system. The nominal operating voltages for the ICs are typically known because most ICs are manufactured to meet industry standards for device operation. For example, the nominal supply voltage for transistor-transistor logic (TTL) devices is 5.0 volts while the nominal supply voltage for complementary metal oxide semiconductor (CMOS) devices is 3.3 volts. Ideally, a power supply will deliver the nominal voltage levels with perfect assurance and precision, but power supplies are typically inaccurate due to a number of factors. A typical range of assurance for a power supply is plus or minus five percent. Thus, most ICs are further designed to operate within a range of plus or minus five percent of the nominal voltage.
However, some ICs are less tolerant of power supply inaccuracies, requiring ranges of assurance that are a lot more precise than what are offered by typical off the shelf power supplies, whereas, other ICs may require nominal operating voltages other than the standard TTL and CMOS voltages supported by the off the shelf power supplies. The operating voltage of an IC having either one or both of these characteristics can be supplied by a DC-DC converter that converts a DC output of the power supply into the desired DC operating voltage and/or the desired range of assurance, such as the DC-DC converter disclosed in copending U.S. patent application Ser. No. 08/184,387, filed Jan. 24, 1994, entitled A High Performance DC-DC Converter.
As discussed in the copending application, three critical considerations in designing DC-DC converters for computer systems are efficiency, load transients, and cost. It is inefficient and costly to provide a DC-DC converter to meet each of the different range accuracy and/or nominal operating voltage requirements of the various IC components of a computer system.
Thus, it is desirable to provide a DC-DC converter that can output multiple nominal operating voltages with different ranges of assurance. It is further desirable that the DC-DC converter can accommodate load transients in one or more of its outputs. As will be disclosed in more detail below, the multiple output DC-DC converter of the present invention advantageously achieves these and other desirable results.